Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Available-for-sale debt securities (Details)

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Summary of Significant Accounting Policies - Available-for-sale debt securities (Details)
 12 Months Ended
Dec. 31, 2023
USD ($)
security
Dec. 31, 2022
USD ($)
security
Dec. 31, 2021
USD ($)
Marketable securities      
Proceeds from the maturity or redemption of available-for-sale debt securities $ 210,983,000 $ 166,994,000 $ 224,343,000
Realized gain on available-for-sale debt securities 198,000 0 $ 6,000
Marketable securities - Net of allowance for expected credit losses 0 0  
Cash equivalents      
Marketable securities      
Amortized cost 1,601,000    
Gross unrealized losses (1,000)    
Aggregate estimated fair value 1,600,000    
Marketable securities      
Marketable securities      
Amortized cost 2,940,000 97,501,000  
Gross unrealized gains 7,000 1,000  
Gross unrealized losses   (930,000)  
Aggregate estimated fair value 2,947,000 96,572,000  
Fair market value of investments in an unrealized loss position $ 1,600,000 $ 90,618,000  
Number of available-for-sale securities in an unrealized loss position, less than 12 months | security 1 19  
Unrealized losses, less than 12 months $ (1,000) $ (930,000)  
Corporate Debt Securities Maturity Period Less Than Three Months | Cash equivalents      
Marketable securities      
Amortized cost 1,601,000    
Gross unrealized losses (1,000)    
Aggregate estimated fair value $ 1,600,000    
Corporate Debt Securities Maturity Period Less Than Three Months | Marketable securities      
Marketable securities      
Amortized cost   45,386,000  
Gross unrealized gains    
Gross unrealized losses   (72,000)  
Aggregate estimated fair value   $ 45,314,000  
Corporate Debt Securities Maturity Period Less Than Three Months | Maximum | Cash equivalents      
Marketable securities      
Available for sale securities debt maturity period 3 months    
Corporate Debt Securities Maturity Period Less Than Three Months | Maximum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period   3 months  
U.S. Treasury Securities Maturity Period Less Than Three Months | Marketable securities      
Marketable securities      
Amortized cost   $ 5,953,000  
Gross unrealized gains   1,000  
Aggregate estimated fair value   5,954,000  
Corporate Debt Securities Maturity Period Three Months To One Year | Marketable securities      
Marketable securities      
Amortized cost $ 2,940,000 41,154,000  
Gross unrealized gains 7,000  
Gross unrealized losses   (704,000)  
Aggregate estimated fair value $ 2,947,000 $ 40,450,000  
Corporate Debt Securities Maturity Period Three Months To One Year | Minimum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period   3 months  
Corporate Debt Securities Maturity Period Three Months To One Year | Maximum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period 3 months    
Corporate Debt Securities Maturity Period One Year To Two Years | Minimum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period   3 months  
Corporate Debt Securities Maturity Period One Year To Two Years | Maximum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period   1 year  
Agency Bond Maturity Period One Year To Two Years | Minimum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period   3 months  
Agency Bond Maturity Period One Year To Two Years | Maximum | Marketable securities      
Marketable securities      
Available for sale securities debt maturity period   1 year  
Agency Bond Maturity Period Three Months To One Year | Marketable securities      
Marketable securities      
Amortized cost   $ 5,008,000  
Gross unrealized gains    
Gross unrealized losses   (154,000)  
Aggregate estimated fair value   4,854,000  
Agency Bond Continuous Loss Position For 12 Months or Longer | Marketable securities      
Marketable securities      
Fair market value of investments in an unrealized loss position   $ 4,854,000  
Number of available-for-sale securities in an unrealized loss position, 12 months or longer | security   1  
Unrealized losses, 12 months or longer   $ (154,000)  
Corporate Debt Securities Continuous Loss Position For 12 Months Or Longer | Marketable securities      
Marketable securities      
Fair market value of investments in an unrealized loss position   $ 74,481,000  
Number of available-for-sale securities in an unrealized loss position, 12 months or longer | security   16  
Unrealized losses, 12 months or longer   $ (679,000)  
Corporate Debt Securities Continuous Loss Position For Less Than 12 Months | Marketable securities      
Marketable securities      
Fair market value of investments in an unrealized loss position $ 1,600,000 $ 11,283,000  
Number of available-for-sale securities in an unrealized loss position, less than 12 months | security 1 2  
Unrealized losses, less than 12 months $ (1,000) $ (97,000)